1. Field of the Invention
One aspect of the present invention generally relates to water curable casting tapes and methods of preparing the same.
2. Background Art
There are various types of immobilization tapes and splints available on the market and described in patent literature, but the most widely used are Plaster of Paris tapes and the polyisocyanate tapes. Plaster of Paris casting tapes are basically gauzes (or some other meshed tapes) impregnated with gypsum. They are activated by immersion in water for about a few seconds, and then applied to immobilize joints or fractures before they set hard. The time needed for them to set hard is defined as the set-time, and it can range from about 5 to about 20 minutes depending on the additives present in Plaster of Paris. Despite many deficiencies, Plaster of Paris immobilization tapes are still widely utilized due to their low cost and good moldability. Their main disadvantages are relatively poor strength to weight ratio that results in bulky and heavy casts, and relatively poor resistance to water that restrict contact with water. In addition, Plaster of Paris tapes often have poor air permeability, which often causes skin irritation.
More recently, synthetic reactive polyurethane casting tapes were developed, which are comprised of a NCO-polyurethane prepolymer (and additives) coated onto mesh-tape (fiberglass, polyester, etc). These tapes are also activated by immersion in water, which reacts with isocyanate (usually in the presence of catalyst) with the set-time of typically about 3 to about 6 minutes. Cured polyisocyanate casts typically have good resistance to water and significantly higher strength to weight ratio than Plaster of Paris tapes. However, they are typically more expensive than Plaster of Paris immobilization tapes. Other disadvantages include that the reaction of isocyanate and water is exothermic, which may cause burns, shelf instability (due to sensitivity of isocyanate to moisture), and somewhat inferior moldability than that of the Plaster of Paris immobilization tapes.
In light of the foregoing, there is a need for orthopedics immobilization casts that combine good properties of Plaster of Paris casts, i.e. good moldability, and good properties of isocyanate casts, i.e. good strength to weight ratio and resistance to water.